The invention concerns a method for the operation of a carbonization or coking plant, with which the coke furnaces are charged periodically with pre-heated coal, and the generated coke is subjected to a dry cooling by means of a gaseous cooling medium, and the heat discharged from the dry cooling of the coke is used directly or indirectly for pre-heating of the coal.
The invention further concerns a special travelling bed drier, which can be employed advantageously for pre-heating the coal with use of the method.
With processes of this type it is already known to connect the plants for the dry cooling of the coke and for the pre-heating of the coal with each other through a common gas circulation. Such a process is described in German Offenlegungsschrift No. DE-OS 23 04 541, corresponding to U.S. Pat. No. 3,728,230, FIG. 8. Therewith it is provided that the hot gas leaving the coke dry cooler is so led collectively, after appropriate cooling and dust removal, from below into the coal pre-heater, that the wet coal introduced from above is presented in the form of a fluidized bed. In connection therewith, the gas leaving from the top of the coal pre-heater is led again into the lower part of the coke dry cooler. With the manner of operation as outlined, with which the coal to be preheated is led into direct contact with the gas from the coke dry cooler, indeed, however, considerable difficulties can occur in practice, because the circulating gas stream is led back into the coke dry cooler with the entire steam content which it has absorbed from the coal pre-heater. As a result of the high steam content of the gas led in circulation, water gas forms to a considerable extent on the hot coke. Through this water gas reaction, however, on the one hand a not inconsiderable consumption of the red-hot coke is caused and, on the other hand, the explosive water gas produced naturally also brings forth considerable problems with regard to operational safety.
A method of the mentioned type is known from German Auslegeschrift No. DE-AS 2342184, corresponding to U.S. Pat. No. 3,800,427, with which the circulation gas of the coke dry cooling is utilized initially in a heat exchanger (waste-heat boiler) for the generation of steam, which is used not only as heating medium but also as flowing bed medium for the pre-heating of the coal. The pre-heating of the coal follows therewith in a single stage in an indirectly heated fluidized bed drier, so that a very intensive heat supply is necessary, which itself, based upon experience, disadvantageously affects the condition of the coal. It is thus possible for there to occur an agglomeration or adhering of the coal to the heating tubes of the fluidized bed drier. Likewise can result a local overheating of the coal particles, whereby changes in the technical coking characteristics can take place.